1. Field of the Invention
The present invention relates generally to a device and method for controlling a receiving amplifier in a radio terminal, and in particular, to a device and method for preventing performance degradation of a radio terminal due to cross modulation occurring in a receiver.
2. Description of the Related Art
FIG. 1 shows a receiver of an existing radio terminal. As illustrated, the radio terminal receives not only a pure signal but also a noise signal at a low noise amplifier 130, so that there occurs cross modulation in the low noise amplifier 130. In addition, when a receiver shares an antenna with a transmitter using a duplexer (not shown), the radio terminal has the following problems. Since the duplexer cannot completely isolate the receiver from the transmitter, a transmission signal output from the transmitter (not shown) may be induced into the low noise amplifier 130 of the receiver, causing cross modulation. The cross modulation decreases the performance of the radio terminal.
Thus, the receiver cannot properly decode a received signal having low strength. To solve this problem, it is necessary to improve performance of a receiving amplifier. A simple method of improving performance of the receiving amplifier is to increase input current so as to improve linearity of the amplifier. However, in the prior art device, a constant current is applied to the amplifier, resulting in inefficient current consumption. Therefore, receiving performance cannot adapt to the radio environment, thereby causing a data loss.
It is, therefore, an object of the present invention to provide a device and method for improving receiving performance of a radio terminal.
It is another object of the present invention to provide a device and method for decreasing power consumption of a radio terminal.
It is further another object of the present invention to provide a device and method for adaptively controlling performance of an amplifier according to a radio environment.
It is still further another object of the present invention to provide a device and method for performing demodulation with minimized signal loss.
It is yet another object of the present invention to provide a device and method for reducing current consumption with minimized signal loss.
To achieve the above objects, there is disclosed a device for controlling a receiving amplifier in a radio-terminal. The device comprises at least one amplifier for amplifying an input signal, the linearity of the amplifier being dependent on an amount of current supplied thereto; a received signal strength indicator (RSSI) measurer for measuring RSSI of the input signal; a variable power supply for controlling an amount of the current supplied to the amplifier in response to a control signal; a signal quality analyzer for measuring a quality of the input signal; and a power controller for generating said control signal according to a transmission/reception mode, the measured RSSI and the measured signal quality. The amplifier includes a low noise amplifier and an intermediate frequency (IF) amplifier.